The invention described herein arose in the course of, or under, Contract No. DE-AC03-SF00098 between the United States Department of Energy and the University of California for the operation of the Lawrence Berkeley Laboratory.
1. Field of the Invention
This invention relates to the formation of a thin film homogeneous oxide solid phase of catalytically active materials and a method of making same. More particularly this invention relates to the formation, by laser ablation, of a thin film homogeneous oxide solid phase reaction product of catalytically active materials comprising one or more alkali metals, one or more alkaline earth metals, and one or more Group VIII transition metals.
2. Description of the Related Art
Materials having catalytic activity have been previously formed by thermal reaction of the oxides and/or salts of an alkali metal, an alkaline earth metal, and an Group VIII metal. For example, mixtures of potassium oxide, calcium oxide, and nickel oxide have been physically formed and then heated to form products which contain, potassium, calcium, nickel, and oxygen, and which exhibits varying amounts of catalytic activity for reactions such as the gasification of carbon solids, and/or the oxidative coupling of methane.
While the catalytic activity of such thermally produced potassium/calcium/nickel/ oxygen products are of interest, attempts to reliably reproduce such products have only met with limited success. The stoichiometry of a resulting product, as well as the degree of catalytic activity of that particular product, seems to vary from one processing run to the next, despite the use of identical amounts of the same materials and the use of identical processing procedures.
One of the reasons for the failure to be able to reliably reproduce such a product containing an alkali metal appears to be the relative volatility of the alkali metal compound starting material, compared to the vapor pressures of the other starting materials. For example, potassium oxide (K.sub.2 O) decomposes at 350.degree. C. and potassium peroxide (K.sub.2 O.sub.2) melts at 490.degree. C.; compared to a melting point of 2580.degree. C. for calcium oxide (CaO); and a melting point of 1990.degree. C. for nickel oxide (NiO). Thus, it is readily apparent that any attempt to form a product from a mixture of the oxides of potassium, calcium, and nickel by a thermal process will result in a loss of at least a substantial amount of the alkali metal oxide long before the other materials will reach a temperature at which any reaction can occur. Apparently, therefore, what has been formed by the prior art methods is not a homogeneous phase, but rather what may be termed as a solid comprising separate phases of the constituent materials.
Therefore, in the past, one attempting, for example, to form a potassium/calcium/nickel/oxygen product having catalytic activity formed a physical mixture of, for example, the oxides of the respective metals, then heated the physical mixture to, for example, about 800.degree. C., and then tested the resulting product for catalytic activity. If the catalytic activity was sufficient, the product could be used. If the catalytic activity was not sufficient, the inferior product was recycled and the process repeated. Thus, a trial and error process or "empirical method" has been the known manner of producing a potassium/calcium/nickel/oxygen product having catalytic activity. Not surprisingly, such results have not been conducive to the carrying out of further research on such catalytic activity to, for example, optimize the stoichiometric ratios the components for maximum catalytic reactivity, or the reaction parameters needed to producing such a catalyst.
It would, therefore, be desirable to be able to reproducibly form reaction products having catalytic activity, and in various stoichiometric ratios, from the oxides and/or salts of one or more alkali metals, one or more alkaline earth metals, and one or more group VIII transition metals.